1. Field of the Invention
The present invention relates to a telephone set and a method of a response to an incoming call and more particularly to an IP (Internet Protocol) telephone set used to pass a voice signal through a packet network using an internet protocol.
The present application claims priority of Japanese Patent Application No. 2000-145818 filed on May 18, 2000, which is hereby incorporated by reference.
2. Description of the Related Art
In a conventional IP telephone set to pass a voice signal through a packet transmission path using an internet protocol, when a handset is put in an off-hook state or when a monitor of a speaker is turned ON in order to make a response to an incoming call, a signal representing a state change caused by the above operations is transmitted to a network and, in response to this signal, packet data of a voice of a party on the other end is transmitted from the network to a user as a voice. Moreover, the user, after having obtained an instruction transmitted from the network, sends out his/her voice to allow transmission of a speech to the network.
FIG. 3 is a schematic block diagram showing configurations of the conventional IP telephone set. In FIG. 3, an IP telephone set 3 includes a packet network interface 31 used to transmit and receive a packet signal from and to a packet network 100, an unpacketing section 32 used to take out signal receipt controlling data and voice receiving data from a received packet, a packeting section 33 used to packet signal transmission controlling data and voice transmission data, a control section 34 to control a telephone on a whole, a codec 35 used to convert digital voice receiving data into analog voice receiving data and to convert analog voice transmission data to digital voice transmission data, a tone generator 38 used to generate various digital signal voices, a key matrix 36 used to detect key operations of the user, a hook switch 37, a handset 39 used to input and output receiving and transmitting voices, a speaker 40 used to amplify receiving voices and a microphone 41 used to input transmitting voices.
The packet network interface 31 is connected to the packet network 100, the unpacketing section 32 and the packeting section 33. The unpacketing section 32 is connected to the control section 34 and the codec 35. The packeting section 33 is connected to the control section 34 and the codec 35. The key matrix 36 and the hook switch 37 are connected to the control section 34. The tone generator 38 is connected to the control section 34 and the codec 35. The handset 39, speaker 40 and microphone 41 are connected to the codec 35.
FIG. 4 is a diagram showing a control signal sequence at the time of the response to the incoming call in the IP telephone set 3 and the packet network 100. Operations at the time of the response to the incoming call in the IP telephone set 3 and the packet network 100 will be described by referring to FIG. 3 and FIG. 4.
When an instruction to make ringing sounds is transmitted from the packet network 100 to the IP telephone set 3, the instruction is received by the packet network interface 31 and data on the instruction to make ringing sounds is taken out by the unpacketing section 32 from received packets and is transmitted to the control section 34.
An incoming call data generation instructing function section 34a in the control section 34 instructs the tone generator 38 to generate incoming call data and instructs the codec 35 to convert the incoming call data fed from the tone generator 38 into analog incoming call data and to transmit it to the speaker 40. The incoming call data generated by the tone generator 38 is converted into analog signals by the codec 35 and is transmitted as the incoming call from the speaker 40.
The user having confirmed the incoming call puts the handset 39 in an off-hook state. A result of the off-hook operation of the user is transmitted to the hook switch 37 and is detected by the control section 34. The control section 34, when detecting the off-hook operation, instructs the tone generator 38 and the codec 35 to stop the transmission of the incoming call and, at the same time, generates an off-hook signal and transmits the generated signal to the pocketing section 33. The off-hook signal is incorporated into the packet to be transmitted in the pocketing section 33 and is transmitted to the packet network 100 from the packet network interface 31.
From this point, the IP telephone set 3 becomes soundless. Moreover, even if the user starts the transmission of speech signals following the off-hook operation, since the IP telephone set 3 is not prepared for the speech transmission, the transmitting voice is not transmitted to the packet network 100.
Though a voice signal of the party on the other end is transmitted as a response to the off-hook signal from the packet network 100, a delay caused by a traffic in the packet network 100 develops. During this time, a soundless state continues.
When a voice signal of the party on the other end is transmitted from the packet network 100, the voice signal is received by the packet network interface 31 and the voice signal of the party on the other end is taken out from received packets by the unpacketing section 32 and is transmitted to the codec 35. The codec 35 converts the voice signal of the party on the other end into analog voice signals and a voice receiving section (not shown) of the handset 39 transmits the converted voice signal to the user, thus enabling the user to hear the voice of the party on the other end.
When a speech transmission permitting signal is transmitted as a response to the off-hook signal from the packet network 100, the a speech transmission permitting signal is received by the packet network interface 31 and the speech transmission permitting signal is taken out from received packets by the unpacketing section 32 and is transmitted to the control section 34.
The control section 34, when having received the speech transmission permitting signal, instructs the codec 35 to transmit the transmitting voice of the user which has been input from a transmitting section (not shown) of the handset 39. In the codec 35, the analog transmitting voice fed from the handset 39 is converted into digital transmitting data and is then transmitted to the packeting section 33. The transmitting data is incorporated in the packet to be transmitted by the packeting section 33 and is transmitted as the speech transmitting voice signal, from the packet network interface 31 to the packet network 100.
The conventional IP telephone set has a problem in that, an arrival of the voice of the party on the other end, in response to the off-hook operation at the time of the incoming call, is delayed due to a traffic condition in the packet network and, during the delay, the user, though having put the IP telephone set in the off-hook state, does not hear the voice of the party on the other end and the IP telephone becomes soundless, thus causing the user to have the distrust in operations of the IP telephone set.
The conventional IP telephone set has another problem in that, an arrival of the speech transmission permitting signal, in response to the off-hook operation at the time of the response to incoming calls, is delayed due to traffic conditions in the packet network and, during the delay, even if the user starts the transmission of speech following the off-hook operation, speech is not transmitted to the party of the other end, thus making it difficult to adjust the timing of starting the transmission of speech.